Role Of Transport System A In The Development Of Neuropathic Pain In Rats

Objective To observe behavioral changes in rat model of neuropathic pain with MeAIB injected intrathecally, and analysis the relationship between and transport system A and neuropathic pain(NP) in rats.Methods Forty-two adult male SD rats weighing200-230g were randomly divided into7groups(n=6each):I control group(group C); II sham operation group(group S); group III NP; IV-W0.1,0.3,0.5and0.7mmol/L a-(methylamino)isobutyric acid (MeAIB), an inhibitor of system A)group(group Ml-4). In group C no operation was performed. In group S the sciatic nerve was only exposed but not ligated. NP was induced by ligation of the tibial nerve and commom peroneal nerve according to the technique described by Dixon. After the establishment of the model, intrathecal PBS50ul was injected in group NP, IT0.1,0.3,0.5and0.7mmol/L MeAIB50ul was injected intrathecally in group M1-4. Mechanical pain threshold, heat hyperalgesia and cold allodynia was measured1week before ligation(T0, baseline), three to four days after ligation(T1) and15min(T2),1.5h(T3) and3h(T4) after injection of MeAIB. In another group, rats were killed at T2and the lumbar segment of the spinal cord was removed for determination of the co-expression of glial fibrillary acidic protein(GFAP) and Glutamine(Gln) and the co-expression of neuron-specific nuclear protein(NeuN)and Glutamine in the dorsal horn.Results (1) Mechanical pain threshold:it was significantly higher at T2in group M1-4compare with group NP, and came back gradually at T3-4(P<0.05).(2) Heat hyperalgesia:there was no significant difference in the withdrawal and duration in all groups(P>0.05).(3) Cold allodynia(response frequence):Compared with group NP,the response frequence,which was significantly increased at T1(P<0.05),was of no difference at T2-4in group M1-4(P>0.05).(4) Immunofluorescence staining:Calculating the mean density of the co-expression area, compare that with group PBS, the co-expression of (GFAP/Gln) was significantly lower in group M1-M4(P<0.001),and compare with group M1,from group M2to M4are on a declining trend(P<0.05);Except group M1, the co-expression of (NeuN/Gln) was significantly lower in group M2-M4compare with group PBS(P<0.05), and compare with group M1,from group M2to M4are on a declining trend(P<0.05).Conclusion Transport system A in the spinal cord is involved in the development of neuropathic pain in rats.